The allocation of inorganic nitrogen ( 15 NH4+) to soil, microbial and plant biomass in an Arctic salt marsh

Abstract

This study has demonstrated, through the shared distribution of a single resource (15 NH4+), that plants and soil microbes compete for inorganic N in a N-limited system. At La Perouse Bay, soil microorganisms out-compete plants for this resource, but their competitive advantage is dampened relative to microorganisms in other Arctic ecosystems by the effects of goose grazing that promote plant growth via the addition of faeces. There is a seasonal displacement of N allocation, as microbes continue to mineralize and slowly immobalize nitrogen in the winter. Loss of vegetation, as a result of goose grabbing, has led to changes in soil characteristics, including high salinity and low redox potentials. These edaphic conditions may dampen N-uptake by soil microoganisms in these disturbed soils. Seasonal grazing effects interact to contribute to a large potential N loss from these soils, altough this is minimized by the apparent abiotic fixation of inorganic N.